Algebraic description of spacetime foam

A mathematical formalism for treating spacetime topology as a quantum observable is provided. We describe spacetime foam entirely in algebraic terms. To implement the correspondence principle we express the classical spacetime manifold of general relativity and the commutative coordinates of its events by means of appropriate limit constructions.Comment: 34 pages, LaTeX2e, the section concerning classical spacetimes in the limit essentially correcte

Impact of a single nucleotide polymorphism on the 3D protein structure and ubiquitination activity of E3 ubiquitin ligase arkadia

Single nucleotide polymorphisms (SNPs) are genetic variations which can play a vital role in the study of human health. SNP studies are often used to identify point mutations that are associated with diseases. Arkadia (RNF111) is an E3 ubiquitin ligase that enhances transforming growth factor-beta (TGF-β) signaling by targeting negative regulators for degradation. Dysregulation of the TGF-β pathway is implicated in cancer because it exhibits tumor suppressive activity in normal cells while in tumor cells it promotes invasiveness and metastasis. Τhe SNP CGT > TGT generated an amino-acid (aa) substitution of Arginine 957 to Cysteine on the enzymatic RING domain of Arkadia. This was more prevalent in a tumor than in a normal tissue sample of a patient with colorectal cancer. This prompted us to investigate the effect of this mutation in the structure and activity of Arkadia RING. We used nuclear magnetic resonance (NMR) to analyze at an atomic-level the structural and dynamic properties of the R957C Arkadia RING domain, while ubiquitination and luciferase assays provided information about its enzymatic functionality. Our study showed that the R957C mutation changed the electrostatic properties of the RING domain however, without significant effects on the structure of its core region. However, the functional studies revealed that the R957C Arkadia exhibits significantly increased enzymatic activity supporting literature data that Arkadia within tumor cells promotes aggressive and metastatic behavior

`Third' Quantization of Vacuum Einstein Gravity and Free Yang-Mills Theories

Based on the algebraico-categorical (:sheaf-theoretic and sheaf cohomological) conceptual and technical machinery of Abstract Differential Geometry, a new, genuinely background spacetime manifold independent, field quantization scenario for vacuum Einstein gravity and free Yang-Mills theories is introduced. The scheme is coined `third quantization' and, although it formally appears to follow a canonical route, it is fully covariant, because it is an expressly functorial `procedure'. Various current and future Quantum Gravity research issues are discussed under the light of 3rd-quantization. A postscript gives a brief account of this author's personal encounters with Rafael Sorkin and his work.Comment: 43 pages; latest version contributed to a fest-volume celebrating Rafael Sorkin's 60th birthday (Erratum: in earlier versions I had wrongly written that the Editor for this volume is Daniele Oriti, with CUP as publisher. I apologize for the mistake.

`Iconoclastic', Categorical Quantum Gravity

This is a two-part, `2-in-1' paper. In Part I, the introductory talk at `Glafka--2004: Iconoclastic Approaches to Quantum Gravity' international theoretical physics conference is presented in paper form (without references). In Part II, the more technical talk, originally titled ``Abstract Differential Geometric Excursion to Classical and Quantum Gravity'', is presented in paper form (with citations). The two parts are closely entwined, as Part I makes general motivating remarks for Part II.Comment: 34 pages, in paper form 2 talks given at ``Glafka--2004: Iconoclastic Approaches to Quantum Gravity'' international theoretical physics conference, Athens, Greece (summer 2004

Hybrid integration of microfabricated chemοcapacitor arrays with miniaturized read-out electronics towards low-power gas sensing module

AbstractA hybrid gas sensing module consisting of an array of 8 polymer coated capacitive sensors and low power read-out electronics is introduced. The chemocapacitor array is fabricated with standard microelectronics/micromachining processes allowing for the realization of planar InterDigitated Electrodes (IDEs). The read-out electronics sub- module consists of an analog multiplexer for the sequential measurement of the sensor array elements, a capacitance to 24-bit converter and a USB to I2C interface. The compact hybrid module has been successfully applied in the detection of sub-100ppm concentrations of p-xylene and toluene. The responses to various humidity levels have been also evaluated

Convergence of IP-based and optical transport networks

Today Network and Service Providers are aware of the increasing data traffic volumes and as such they are strategically moving investigations toward a single integrated voice and data infrastructure. In this context IP is gaining the role of the integration layer for multiple services. Nevetheless incumbent NSPs that build a multi-service IP network are going to need connectivity to its preexisting legacy networks (e.g. ATM. SONET, SDH). This reason motivates the introduction of a client-independent Optical Transport Network (OTN) as a missing link to guarantee a smooth evolution from legacy networks to a data-centric OTN. The scope of this paper is to give some guidelines about the definition of functionality and architectures of a multilayers infrastructure supporting the transport of data and circuit-based services. Particularly, the identification of the different service requirements, as well as the understanding of the allowed degradation, provide a picture of the needed survivability mechanism of IP over OTN scenarios

Mixed-effects height prediction model for Juniperus procera trees from a Dry Afromontane Forest in Ethiopia.

Tree height is a crucial variable in forestry science. In the current study, an accurate height prediction model for Juniperus procera Hochst. ex Endl. trees were developed, using a nonlinear mixed-effects modeling approach on 1215 observations from 101 randomly established plots in the Chilimo Dry Afromontane Forest in Ethiopia. After comparing 14 nonlinear models, the most appropriate base model was selected and expanded as a mixed-effects model, using the sample plot as a grouping factor, and adding stand-level variables to increase the model’s prediction ability. Using a completely independent dataset of observations, the best sampling alternative for calibration was determined using goodness-of-fit criteria. Our findings revealed that the Michaelis–Menten model outperformed the other models, while the expansion to the mixed-effects model significantly improved the height prediction. On the other hand, incorporating the quadratic mean diameter and the stem density slightly improved the model’s prediction ability. The fixed-effects of the selected model can also be used to predict the mean height of Juniperus procera trees as a marginal solution. The calibration response revealed that a systematic selection of the three largest-diameter trees at the plot level is the most effective for random effect estimation across new plots or stands

Comparison of the Electronic Structures and Energetics of Ferroelectric LiNbO3 and LiTaO3

This paper explains the origin of the ferroelectric instability in LiNbO3 and LiTaO3 and compares the electronic structures and energetics of the two materials.Comment: 31 pages, 11 Postscript figure